<!DOCTYPE html>
<html>
  <head>
    <style>
      body, html {
        margin: 0;
      }

      #scroller {
        position: absolute;
        clip: rect(0, 1000px, 1000px, 0);
        width: 300px;
        height: 300px;
        overflow: auto;
      }

      #spacer {
        height: 1000px;
      }

      #topbox {
        height: 5px;
        width: 100%;
        background-color: green;
      }
    </style>
  </head>
  <body>
    <div id="scroller">
      <div id="topbox"></div>
      <div id="spacer"></div>
    </div>
  </body>
</html>
